U.S. patent number 8,587,752 [Application Number 12/638,117] was granted by the patent office on 2013-11-19 for liquid crystal display device with light shielding covering two-layered common electrode.
This patent grant is currently assigned to NLT Technologies, Ltd.. The grantee listed for this patent is Taku Kawasaki, Shinichi Nishida, Yoshikazu Sakaguchi, Sounosuke Takahashi, Takahiko Watanabe. Invention is credited to Taku Kawasaki, Shinichi Nishida, Yoshikazu Sakaguchi, Sounosuke Takahashi, Takahiko Watanabe.
United States Patent |
8,587,752 |
Nishida , et al. |
November 19, 2013 |
Liquid crystal display device with light shielding covering
two-layered common electrode
Abstract
A normally-black active-matrix-type liquid crystal display
device comprises a first substrate having color layers of three or
more colors and a second substrate on which an active-matrix array
is formed. The first substrate has a structure, which is devoid of
a black matrix, in which the color layers are stacked in a frame
portion surrounding the display area. A first light-shielding layer
in which color layers of three of more colors are stacked is formed
on the frame portion on a side of the display area from which
scanning lines are led out and on a side of the display area from
which data lines are led out, from among four sides of the display
area. A second light-shielding layer in which color layers of two
colors are built up is formed on the frame portion on at least one
side of the other remaining sides of the display area.
Inventors: |
Nishida; Shinichi (Kanagawa,
JP), Takahashi; Sounosuke (Kanagawa, JP),
Watanabe; Takahiko (Kanagawa, JP), Sakaguchi;
Yoshikazu (Kanagawa, JP), Kawasaki; Taku
(Kanagawa, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Nishida; Shinichi
Takahashi; Sounosuke
Watanabe; Takahiko
Sakaguchi; Yoshikazu
Kawasaki; Taku |
Kanagawa
Kanagawa
Kanagawa
Kanagawa
Kanagawa |
N/A
N/A
N/A
N/A
N/A |
JP
JP
JP
JP
JP |
|
|
Assignee: |
NLT Technologies, Ltd.
(Kanagawa, JP)
|
Family
ID: |
42240107 |
Appl.
No.: |
12/638,117 |
Filed: |
December 15, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100149467 A1 |
Jun 17, 2010 |
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Foreign Application Priority Data
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Dec 15, 2008 [JP] |
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2008-318630 |
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Current U.S.
Class: |
349/110; 349/111;
349/113; 345/88; 349/106 |
Current CPC
Class: |
G02F
1/133512 (20130101); G02F 1/1362 (20130101) |
Current International
Class: |
G02F
1/1333 (20060101); G02F 1/1335 (20060101); G09G
3/36 (20060101) |
Field of
Search: |
;349/106,110,111,113 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1305120 |
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Jul 2001 |
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CN |
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2000-029014 |
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Jan 2000 |
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JP |
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2003-014917 |
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Jan 2003 |
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JP |
|
Other References
Chinese Official Action dated Dec. 5, 2012 issued by the Chinese
Patent Office in Chinese Patent Application No. 200910260466.4, 6
pages. cited by applicant.
|
Primary Examiner: Nguyen; Hoan C
Attorney, Agent or Firm: Young & Thompson
Claims
What is claimed is:
1. An active-matrix liquid crystal display device, the liquid
crystal of which is normally black, comprising: a first substrate
having color layers of three or more colors; and a second substrate
on which an active-matrix array is formed; wherein said first
substrate has a structure, which does not have a black matrix
layer, in which the color layers are stacked in a frame portion
surrounding a display area; a first light-shielding layer in which
color layers of three or more colors are stacked is formed on the
frame portion on a side of the display area from which scanning
lines are led out and on a side of the display area from which data
lines are led out, from among four sides of the display area; a
second light-shielding layer in which color layers of two colors
are stacked is formed on the frame portion on at least one side of
the other remaining sides of the display area; two metal layers to
which a common electrode potential is applied are placed in an area
of the second substrate opposing the second light-shielding layer;
and an insulating layer is placed between the two metal layers.
2. The device according to claim 1, wherein the two colors of the
second light-shielding layer are red and blue.
3. The device according to claim 1, wherein the side of the display
area on which the second light-shielding layer is formed is
provided with an injection hole for injecting liquid crystal.
4. The device according to claim 2, wherein the side of the display
area on which the second light-shielding layer is formed is
provided with an injection hole for injecting liquid crystal.
5. The device according to claim 1, wherein on sides where
scanning-line and data-line leads are present, the frame portion at
a periphery of the display area has the first light-shielding layer
of stacked layers of three or more colors so that light-shielding
performance is excellent even in areas in which light cannot be
blocked by metal electrodes of the active-matrix substrate.
6. The device according to claim 5, wherein on at least one side of
two sides where the scanning-line and data-line lead-out wiring do
not exist has the second light-shielding layer of two superimposed
colors.
7. The device according to claim 1, wherein each color layer has a
thickness on an order of 1.5 .mu.m.
8. The device according to claim 1, wherein each metal layer has a
thickness of about 2500 .ANG..
9. The device according to claim 1, wherein the device has a cell
gap of 3.5 .mu.m.
10. The device according to claim 1, wherein the stacked color
layers substitute for a black matrix.
11. The device according to claim 1, wherein the stacked color
layers substitute for a black matrix where the frame portion can be
positively shielded from light while a supply of the common
electrode potential in the second substrate with the active-matrix
array by a low resistance is facilitated.
12. An active-matrix liquid crystal display device, the liquid
crystal of which is normally black, comprising: a first substrate
having color layers of three or more colors; and a second substrate
on which an active-matrix array is formed; wherein said first
substrate has a structure in which the color layers are stacked in
a frame portion surrounding a display area; a first light-shielding
layer in which color layers of three or more colors are stacked is
formed on the frame portion on a side of the display area from
which scanning lines are led out and on a side of the display area
from which data lines are led out, from among four sides of the
display area; a second light-shielding layer in which color layers
of two colors are stacked is formed on the frame portion on at
least one side of the other remaining sides of the display area;
two metal layers to which a common electrode potential is applied
are placed in an area of the second substrate opposing the second
light-shielding layer; and an insulating layer is placed between
the two metal layers, wherein the stacked color layers substitute
for a black matrix.
13. The device according to claim 12, wherein the two colors of the
second light-shielding layer are red and blue.
14. The device according to claim 12, wherein the side of the
display area on which the second light-shielding layer is formed is
provided with an injection hole for injecting liquid crystal.
15. The device according to claim 13, wherein the side of the
display area on which the second light-shielding layer is formed is
provided with an injection hole for injecting liquid crystal.
16. The device according to claim 12, wherein on sides where
scanning-line and data-line leads are present, the frame portion at
a periphery of the display area has the first light-shielding layer
of stacked layers of three or more colors so that light-shielding
performance is excellent even in areas in which light cannot be
blocked by metal electrodes of the active-matrix substrate.
17. The device according to claim 16, wherein on at least one side
of two sides where the scanning-line and data-line lead-out wiring
do not exist has the second light-shielding layer of two
superimposed colors.
18. The device according to claim 12, wherein each color layer has
a thickness on an order of 1.5 .mu.m.
19. The device according to claim 12, wherein each metal layer has
a thickness of about 2500 .ANG..
20. The device according to claim 12, wherein the device has a cell
gap of 3.5 .mu.m.
Description
TECHNICAL FIELD
Reference to Related Application
This application is based upon and claims the benefit of the
priority of Japanese patent application No. 2008-318630, filed on
Dec. 15, 2008, the disclosure of which is incorporated herein in
its entirety by reference thereto.
This invention relates to an active-matrix-type liquid crystal
display device and, more particularly, to an active-matrix-type
liquid crystal display device having a light-shielding structure in
which color layers are stacked and replace a black matrix.
BACKGROUND
There has been strong demand in recent years for a device structure
and manufacturing process that can enable the manufacture, at lower
cost, of an active-matrix-type liquid crystal display device
exhibiting excellent display quality.
For example, in order to block light impinging from the frame
surrounding a display area in a liquid crystal display device, a
light-shielding layer referred to as a "black matrix" is formed on
the side of a substrate having a color filter (a color-filter
substrate) using a metal such as chrome (chrome oxide) or a resin.
For the purpose of lowering cost, however, a technique for
eliminating the black matrix has been proposed.
For example, Patent Documents 1 and 2, cited below, disclose
techniques for forming a light-shielding layer on the frame portion
surrounding the liquid crystal area by stacking colored layers of
at least two colors selected from a plurality thereof.
[Patent Document 1]
Japanese Patent Kokai Publication No. JP2000-290014A
[Patent Document 2]
Japanese Patent Kokai Publication No. JP2003-14917A
SUMMARY
As disclosed in Patent Documents 1 and 2, a technique for forming a
light-shielding structure by stacking a plurality of layers, which
constitute a color filter, without using a black-matrix layer is an
effective method in terms of lowering cost.
With the conventional techniques, however, the frame portion
surrounding the display area of the liquid crystal display device
is formed on all four sides by superimposing three or more colors
or two or more colors. As a result of detailed studies, these
techniques have been found to have the problems set forth
below.
First, in a case where two colors are superimposed to form the
frame on all four sides of the display area, the following problem
arises:
If a normally-black liquid crystal is used, a portion inside the
liquid crystal display device where an alignment-treated alignment
film and polarizers external to the film are present is shielded
from light by these elements, a frame having an attractive
appearance is obtained even with the low OD (Optical Density) value
of two superimposed colors. Normally, however, in order to prevent
a seal and the alignment film from interfering with each other, the
area where the alignment film is formed can only extend a fixed
distance into the interior from the seal formed in order to seal
the liquid crystal inside the cell. As a consequence, the
light-shielding performance on the outer side of the alignment film
is inferior to that on the inner side of the alignment film. With
the low OD value of two superimposed colors, therefore, one can see
through the superimposed colors when the device is viewed in a
darkened environment and hence the quality of the display declines.
In order to compensate for this, placing a metal layer on the side
of the active-matrix substrate has been proposed. However, blocking
the light between wiring traces is extremely difficult and is
essentially impossible on the side where scanning lines are led out
and on the side where the data lines are led out.
On the other hand, in a case where three or more colors are
superimposed to form the frame on all four sides of the display
area, the following problem arises:
In the case of a transverse-field liquid crystal display device, it
is required that the display area be supplied from the periphery
with a common potential using a fairly low resistance value. In
order to thus supply the display area with a common potential using
a low resistance, often two or more metal layers necessary when an
active matrix is formed, namely a metal a layer for forming
scanning lines and a metal layer for forming data lines, are
stacked and placed at the frame portion as common electrode wiring.
Since the metal wiring traces of the two layers thus formed each
have a thickness of about 2500 A, the total film thickness on the
active-matrix substrate is 5000 A greater in comparison with the
portion devoid of the metal wiring layers. Similarly, with regard
to the color-filter substrate, the film thickness of each color
layer is on the order of 1.5 .mu.m. The film thickness of the frame
portion composed of the three stacked color layers, therefore, is 3
.mu.m greater in comparison with the display area having only a
single color layer. When these two substrates are bonded together,
an attempt is made to obtain a value of e.g., 3.5 .mu.m for the
cell gap, namely the distance between the active-matrix substrate
and the color-filter substrate in the display area. At the portion
where the two-layer common electrode wiring and
three-superimposed-color portion are superimposed in such case, the
fact that these have the above-mentioned thicknesses of 5000 A and
3.0 .mu.m, respectively, means that the clearance between the two
members becomes almost zero. As a consequence, the problem which
arises is that the two substrates come into contact, gap uniformity
and liquid crystal encirclement at this portion become
unsatisfactory and an air bubble is formed. Thus there is much to
be desired in the art.
Accordingly, it is a the main object thereof to provide an
active-matrix-type liquid crystal display device having a structure
in which color layers are stacked and substituted for a black
matrix, wherein the frame portion can be positively shielded from
light while supply of a common electrode potential in the
active-matrix substrate by a low resistance is facilitated.
According to the present invention, there is provided an
active-matrix liquid crystal display device, the liquid crystal of
which is normally black, comprising: a first substrate having color
layers of three or more colors; and a second substrate on which an
active-matrix array is formed. The first substrate has a structure,
which is devoid of a black matrix, in which the color layers are
stacked in a frame portion surrounding a display area. A first
light-shielding layer in which color layers of three or more colors
are stacked is formed on the frame portion on a side of the display
area from which scanning lines are led out and on a side of the
display area from which data lines are led out, from among four
sides of the display area. A second light-shielding layer in which
color layers of two colors are stacked is formed on the frame
portion on at least one side of the other remaining sides of the
display area.
Further, the active-matrix liquid crystal display device of the
present invention may be such that two or more metal layers to
which a common electrode potential is applied are placed in an area
of the second substrate opposing the second light-shielding
layer.
Further, the active-matrix liquid crystal display device of the
present invention may be such that the two colors of the second
light-shielding layer are red and blue.
Further, the active-matrix liquid crystal display device of the
present invention may be such that the side of the display area on
which the second light-shielding layer is formed is provided with
an injection hole for injecting liquid crystal.
The meritorious effects of the present invention are summarized as
follows.
In accordance with the present invention, a normally-black
active-matrix-type liquid crystal display device having a structure
devoid of a black-matrix layer is so adapted that the frame portion
thereof can be positively shielded from light while supply of a
common electrode potential in the active-matrix substrate by a low
resistance is facilitated.
Other features and advantages of the present invention will be
apparent from the following description taken in conjunction with
the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTIONS OF THE DRAWINGS
FIG. 1 is a plan view illustrating a liquid crystal display device
according to a first exemplary embodiment of the present
invention;
FIG. 2 is a sectional view illustrating the structure of the liquid
crystal display device according to the first exemplary embodiment
taken along line A-A' of FIG. 1, wherein the section is taken along
data-line lead-out wiring at the frame portion;
FIG. 3 is a sectional view illustrating the structure of the liquid
crystal display device according to the first exemplary embodiment
taken along line B-B' and C-C' of FIG. 1;
FIG. 4 is a plan view illustrating a liquid crystal display device
according to a second exemplary embodiment of the present
invention;
FIG. 5 is a sectional view illustrating the structure of the liquid
crystal display device according to the second exemplary embodiment
taken along line A-A' of FIG. 4, wherein the section is taken along
data-line lead-out wiring at the frame portion;
FIG. 6 is a sectional view illustrating the structure of the liquid
crystal display device according to the second exemplary embodiment
taken along line B-B' of FIG. 4;
FIG. 7 is a sectional view illustrating the structure of the liquid
crystal display device according to the second exemplary embodiment
taken along line C-C' of FIG. 4;
FIG. 8A is a plan view illustrating the arrangement of electrodes
on an array substrate of the liquid crystal display device
according to the first exemplary embodiment; and
FIG. 8B is an enlarged view of an area designated in FIG. 8A in the
plan view illustrating the arrangement of electrodes on the array
substrate of the liquid crystal display device according to the
first exemplary embodiment.
PREFERRED MODE
An active-matrix liquid crystal display device according to the
present invention includes a normally-black liquid crystal and has
a first substrate (a color-filter substrate 10) on which a color
filter has been formed and a second substrate (an array substrate
20) on which an active-matrix array has been formed. Among the four
sides of the display area of the liquid crystal display device,
there is a side having scanning-line lead-out wiring 3 and a side
having data-line lead-out wiring 4. The color-filter substrate 10
is devoid of a black matrix. A light-shielding layer 1, which
includes three or more superimposed colors (layers), is disposed on
the color-filter substrate 10 on a frame portion thereof at the
periphery of the display area, the light-shielding layer 1 being
placed on the side of the device having the scanning-line lead-out
wiring 3 and on the side of the device having the data-line
lead-out wiring 4. A light-shielding layer 2 formed of two
superimposed colors (layers) is disposed on the color-filter
substrate 10 on the frame portion thereof on at least one side of
the other remaining sides of the device.
As a result, on the sides where the scanning-line and data-line
leads are present, the frame portion at the periphery of the
display area has stacked layers of three or more colors so that the
light-shielding performance is excellent even in areas in which
light cannot be blocked by the metal electrodes of the
active-matrix substrate. This means that an excellent frame is
obtained with almost no leakage of light external to an area in
which an alignment film is printed.
Further, the frame portion on at least one side of the two sides
where the scanning-line and data-line lead-out wiring 3, 4,
respectively, do not exist is formed to have the light-shielding
layer 2 consisting of two superimposed colors. As a result, a
satisfactory clearance is obtained between the array substrate 20
and the color-filter substrate 10, and common electrode wiring 21,
22 consisting of two stacked layers, namely a metal layer forming
scanning lines and a metal layer forming data lines, can be placed
in this clearance. By supplying the display area with a common
electrode potential via the common electrode wiring, the common
electrode potential at the display area is stabilized and a problem
such as transverse crosstalk caused by a fluctuation in this
potential can be suppressed. The result is that an excellent
display quality is obtained. Furthermore, the common electrode
wiring 21, 22 placed in the frame portion is made sufficiently
broad so that light which has entered from a backlight will not
pass through the frame portion and be visible to a person looking
at the liquid crystal display device. As a result, inadequate
light-shielding performance of the light-shielding layer 2 composed
of two superimposed colors is compensated for by the
light-shielding effect of the common electrode wiring 21, 22.
Usually, color layers of the three primary colors red (R) 7, green
(G) 6 and blue (B) 8 are used in a color filter. In the case of a
color filter composed of these layers of three colors, three
superimposed colors R, G, B are used at a frame portion where the
scanning-line or data-line lead-out wiring is disposed, and two
superimposed colors R and B are used in the light-shielding layer,
which is composed of two superimposed colors, on at least one side
of the remaining sides. The light-shielding performance of two
superimposed colors among the three colors R, G, B is best when the
two superimposed colors used are R and B. As a result, it is
possible to suppress a decline in display quality caused by light,
which impinges upon the frame portion of two superimposed colors
from the top side (from the direction in which the display is
viewed), passing through the light-shielding layer of two
superimposed colors and re-emerging from the top side upon being
reflected by the metal wiring on the side of the active matrix.
[First Exemplary Embodiment]
Reference will now be had to FIGS. 1 to 3 and to FIGS. 8A and 8B to
describe in detail an active-matrix liquid crystal display device
according to a first exemplary embodiment of the present invention.
FIG. 1 is a plan view illustrating an active-matrix liquid crystal
display device according to this exemplary embodiment, FIG. 2 is a
sectional view taken along line A-A' of FIG. 1, FIG. 3 is a
sectional view taken along line B-B' of FIG. 1, FIG. 8A is a plan
view illustrating the arrangement of electrodes on an array
substrate, and FIG. 8B is an enlarged plan view of an area shown in
FIG. 8A.
As illustrated in FIG. 2, the liquid crystal display device of this
exemplary embodiment includes the array substrate 20 having an
array pattern in which pixels having switching elements such as
TFTs (Thin-Film Transistors) are arranged in the form of a matrix;
the color-filter substrate 10 opposing the array substrate 20;
liquid crystal 17 sandwiched between the substrates 10 and 20; and
a seal 19 joining these two substrates and sealing in the liquid
crystal 17. In a display area of the color-filter substrate 10,
color layers of each of the colors are disposed in opposition to
the pixels of the array substrate 20, one or a plurality of color
layers are stacked on the frame portion at the periphery of the
display area 15, and an overcoat 9 is formed so as to cover these
color layers.
On the side having the scanning-line lead-out wiring 3 and on the
side having the data-line lead-out wiring 4, the frame portion at
the periphery of the display area 15 forms the light-shielding
layer 1 composed of the three superimposed colors R, G, B, and the
frame portion on the other two sides forms the light-shielding
layer 2 composed of the two superimposed colors R and B, as
illustrated in FIG. 1.
At the frame portions formed by the two colors, the common
electrode wiring 21, 22, which is supplied with a common potential,
is formed on the side of the array substrate 20 and comprises
stacked metal layers, namely a first metal layer forming the
scanning lines and a second metal layer forming the data lines,
respectively. Since the common electrode wiring formed by two
layers has a low resistance (also with sufficient width) the
interior of the display can be supplied with a stable common
potential. As a result, a problem such as transverse crosstalk that
accompanies a fluctuation in common potential can be
suppressed.
As illustrated in FIG. 8A, a common potential is input to common
electrode wiring 26 from a common-potential input terminal 28
provided at the corner of the side having the data-line lead-out
wiring 4 and the side having the scanning-line lead-out wiring 3.
Since the common electrode wiring 26 is formed by two layers of
metal, a common potential can be transmitted at low resistance.
Common signal line 27 is led out from the common electrode wiring
26 and the common potential is supplied up to the display area. As
illustrated in FIG. 8B, the common potential is connected to a
common electrode 35 of each pixel via a through-hole 33 for making
contact with the common electrode with which each pixel is
provided.
In this exemplary embodiment, switching of the liquid crystal is
carried out by IPS (In-Plane Switching) whereby transmitted light
is controlled by applying a transverse electric field between the
potential of a pixel electrode 34, which is supplied via a
thin-film transistor and a through-hole 32 for the pixel electrode,
and the potential of the common electrode 35.
With IPS, a high-aperture-ratio display can be obtained by
shielding scanning lines 25 and data lines 24 using an ITO (Indium
Tin Oxide) common electrode 30 in the display area, as illustrated
in FIG. 8B. In such case it is especially required that the common
potential be supplied from the periphery at a low resistance owing
to a capacitive load ascribable to capacitive coupling between the
common electrode 30 and the scanning lines 25 and data lines 24.
Since the two layers of metal wiring provided in the frame portion
have a low resistance under these circumstances, this arrangement
is very effective and is accompanied by the fact that the problem
of transverse crosstalk can be markedly suppressed.
Further, the common electrode wiring 26 is placed in substantially
the entire area, outside the display area, through which is
transmitted the backlight that passes through in the direction from
which the display is viewed. As a result, the low OD ascribable to
the light-shielding layer composed of the two superimposed color
layers can be compensated for by the common electrode wiring 21,
22.
On the other hand, since the light-shielding layer of the frame on
the sides where the scanning-line lead-out wiring 3 and data-line
lead-out wiring 4 reside is formed by three superimposed colors,
the light-shielding performance is sufficiently high and even light
that passes through the incomplete alignment area where the
alignment film has not been formed is blocked sufficiently by the
light-shielding layer of three superimposed colors.
In this exemplary embodiment, for instance, the thickness of each
layer of the R, G, B layers was made 1.5 .mu.m and the thickness of
each metal layer of the metal layers of the scanning lines and data
lines was made 0.25 .mu.m. The cell gap of the display area was
made 3.5 .mu.m, and the film thickness of the ITO comprising the
uppermost layer was made 0.04 .mu.m, by way of example.
As a result, at the frame portion on the sides having the
scanning-line lead-out wiring 3 and data-line lead-out wiring 4,
the array side of the area in which each of the lead-out wiring
traces resides was 0.29 .mu.m thicker than the display area and the
color-filter side was 3.0 .mu.m thicker. At the frame portion,
therefore, the cell gap was narrowed by 3.29 .mu.m so that the
clearance obtained between the array substrate and the color-filter
substrate was 2.1 .mu.m. This clearance was satisfactory and
afforded an excellent display.
Further, on the two sides devoid of the scanning-line lead-out
wiring 3 and data-line lead-out wiring 4, the array side was 0.5
.mu.m thicker than the display area and the side of the
color-filter substrate was 1.5 .mu.m thicker. At the frame portion,
therefore, the cell gap was narrowed by 2.0 .mu.m so that the
clearance obtained between the array substrate and the color-filter
substrate was 1.5 .mu.m. This clearance was satisfactory and
afforded an excellent display without interference arising when the
gap was formed.
A method of manufacturing the liquid crystal display device having
the structure set forth above will now be described.
The method of manufacturing the color-filter substrate 10 will be
described first.
First, after a coating of a resist which will be the G-color layer
6 is applied, exposure to light is performed using an exposure mask
that includes a pattern comprising the G-color layer pattern of the
display area 15 and the frame portion that includes the
scanning-line and data-line lead-out wiring 3, 4. This is followed
by development and firing, thereby forming the G-color layer 6 to a
thickness of 1.5 .mu.m.
Next, after a coating of a resist which will be the R-color layer 7
is applied, exposure to light is performed using an exposure mask
that includes a pattern comprising the R-color layer pattern of the
display area 15 and the frame portion of the four sides. This is
followed by development and firing, thereby forming the R-color
layer 7 to a thickness of 1.5 .mu.m.
Furthermore, after a coating of a resist which will be the B-color
layer 8 is applied, exposure to light is performed using an
exposure mask that includes a pattern comprising the B-color layer
pattern of the display area 15 and the frame portion of the four
sides. This is followed by development and firing, thereby forming
the B-color layer 8 to a thickness of 1.5 .mu.m.
Next, these color layers are coated to a thickness of 1.0 .mu.m
with a transparent acrylic resin which will be the overcoat 9. This
is following by firing. Next, columnar spacers are formed thereon
using an acrylic resin. The color-filter substrate 10 is obtained
as a result.
In the description rendered above, a case where the color layers of
the three colors are stacked in the order G, R, B. However, the
stacking order can be changed. Further, the columnar spacers may be
formed on the side of the array substrate 20, or spherical spacers
may be used rather than forming columnar spacers. Further, the film
thickness of the color layers can be adjusted in conformity with
the chromaticity sought.
A method of manufacturing the array substrate 20 will be described
next.
This method is a method of manufacture that is entirely the same as
that of an active-matrix array substrate in which the switching
elements are TFTs using the usual a-Si. For example, the array
substrate 20 can be manufactured through the procedure set forth
below.
First, a 2500-A first metal layer (an opaque metal) which will be
the scanning lines 25 and common-signal line 27 is worked into a
prescribed pattern. At this time the shape of the common electrode
wiring 26 of the frame portion on the side opposing the side of the
scanning-line leads and on the side opposing the side of the
data-line leads.
After a gate insulating film 12 and a thin-film semiconductor layer
31 are formed, the thin-film semiconductor layer 31 is formed into
island shapes only in a portion which will be the switching
elements.
Next, a 2500-A second metal layer which will be the data lines 24
is worked into a prescribed pattern and an island-shaped contact
layer of the thin-film semiconductor layer 31 is etched using this
pattern.
Furthermore, after an insulating film which will be a passivation
film 13 is formed, a though-hole for contact is formed and
interdigitated electrodes comprising the pixel electrode 34 and
common electrode 35 consisting of 400-A ITO (Indium Tin Oxide) are
formed thereon. The pixel electrode 34 is connected via a
though-hole 32 to the drain electrode of the thin-film transistor
formed by the second metal layer, and the common electrode 35 is
connected to the common-signal line 27 formed by the first metal
layer.
In the frame portion where the scanning-line lead-out wiring 3 and
data-line lead-out wiring 4 resides, the scanning-line lead-out
wiring 3 and data-line lead-out wiring 4 is suitably shielded by an
ITO transparent electrode 23 of the uppermost layer, to which the
common potential is applied, in order to prevent the director of
the liquid crystal from rotating owing to the influence of a
potential difference between these wiring traces, as a result of
which the light-shielding ability would no longer be maintained
when the device is in the non-operating state. The ITO transparent
electrode 23 is connected to the common potential.
After an alignment film 16 is formed between the color-filter
substrate 10 and array substrate 20 formed in the manner described
above, these are bonded together and liquid crystal 17 is injected
between them and sealed in. The liquid crystal 17 is homogeneously
oriented and the polarizer is formed by crossed Nicols so as to be
normally black. The liquid crystal is in the so-called IPS mode in
which it is driven by an electric field, which is parallel to the
substrates, produced across the pixel electrode 34 and common
electrode 35.
In this exemplary embodiment, an injection hole 5 used when the
liquid crystal is injected is provided in the
two-superimposed-color side of the frame opposite the side on which
the scanning-line lead-out wiring 3 exists. The liquid crystal is
injected from the hole 5 by the vacuum injection method. When the
liquid crystal 17 enters the interior of the cell, the fact that
the clearance between the array substrate 20 and color-filter
substrate 10 is sufficient means that injection time is short,
problems such as injection failure do not occur and panel formation
is facilitated.
The alignment film 16 is formed, for instance, approximately 0.7 mm
distant from the seal printing area in order to avoid interference
with the seal 19. As a result, although entrant light from the
backlight also passes through the region of incomplete alignment
outside the alignment-film printing area, the light-shielding layer
1 of three superimposed colors presents an adequate light-shielding
ability and, hence, the excellent quality of the frame portion is
maintained.
Finally, polarizers 11, 14 are bonded to both sides and the
prescribed circuitry is connected to the liquid crystal panel,
whereby the liquid crystal display device of this exemplary
embodiment is obtained.
Thus, a satisfactory light-shielding performance is provided with
the frame on the display-area sides having the scanning-line
lead-out wiring 3 and data-line lead-out wiring 4 being made the
light-shielding layer 1 of three superimposed colors. On the side
of the array substrate 20, the common electrode wiring 21, 22
comprising the stacked metal layers of the first and second metal
layers are disposed with the other sides of the display area being
made the light-shielding layer 2 of two superimposed colors. A
common potential is supplied to the display area stably and, at the
same time, the inadequate light-shielding performance of the
light-shielding layer 2 of two superimposed colors on the
color-filter side is compensated for by the light-shielding
performance of the common electrode wiring 21, 22.
By virtue of the foregoing arrangement, the frame on all four sides
of the display area can be provided with a satisfactory
light-shielding performance and an excellent display quality can be
obtained.
[Second Exemplary Embodiment]
Next, an active-matrix liquid crystal display device according to a
second exemplary embodiment of the present invention will be
described with reference to FIGS. 4 to 6. FIG. 4 is a plan view
illustrating the arrangement of a frame of an active-matrix liquid
crystal display device according to this exemplary embodiment, FIG.
5 is a sectional view taken along line A-A' of FIG. 4, FIG. 6 is a
sectional view taken along line B-B' of FIG. 4, and FIG. 7 is a
sectional view taken along line C-C' of FIG. 4.
In the first exemplary embodiment, only the frame portion on the
side having the scanning-line lead-out wiring 3 and on the side
having the data-line lead-out wiring 4 are formed to have the
light-shielding layer 1 composed of the three superimposed colors
R, G, B. By contrast, in this exemplary embodiment, as shown in
FIG. 4, the frame portion on the side opposite the side having the
data-line lead-out wiring 4 is also formed to have the
light-shielding layer 1 composed of the three superimposed colors
R, G, B. Only the frame portion on the single remaining side is
formed to have the light-shielding layer 2 composed of the two
superimposed colors R and B.
In conformity with this arrangement, the common electrode wiring
21, 22 comprising the stacked layers of the first metal layer and
second metal layer is disposed only at the light-shielding layer 2
composed of the two superimposed colors R and B.
The array side on the display-section side opposite the
display-section side having the data-line lead-out wiring 4 need
not be provided with any metal wiring whatsoever. Further, this
array side may be provided with common electrode wiring (21 or 22
only) comprising only one metal layer, namely the first metal layer
or the second metal layer.
This liquid crystal display device can be manufactured by a method
similar to that of the first exemplary embodiment merely by
replacing the wiring patterns and frame color-overlap patterns with
those of the second exemplary embodiment.
By virtue of the above-described arrangement, in a manner similar
to that of the first exemplary embodiment, the light-shielding
performance on the side of the color filter is sufficiently high at
the frame portion on the sides formed to have the three
superimposed colors, and the low-resistance common electrode wiring
21, 22 formed by two layers of metal wiring stabilizes the common
potential of the display area at the frame portion on the side
formed to have the two superimposed colors and compensates for the
light-shielding performance of the light-shielding layer 2 composed
of two superimposed colors. As a result, the frame on all four
sides of the display area can be provided with an excellent
appearance. Moreover, since the clearance between the side of the
array substrate 20 and the side of the color-filter substrate 10
can be made sufficiently large, an excellent display is obtained
without interference occurring when the cell gap is formed.
In each of the foregoing exemplary embodiments, a color-layer
pattern composed of the three colors R, G, B is described. However,
the present invention is not limited to these exemplary embodiments
and can be applied in a case where a color-layer pattern of four or
more colors is formed and is also similarly applicable to three
primary colors other than R, G, B.
Examples of utilization of the present invention are not limited to
active-matrix liquid crystal display devices using the IPS method
but also include a normally-black active-matrix liquid crystal
display device having a similar color filter of light-shielding
layers of superimposed colors, as well as equipment using this
liquid crystal display device, such as a computer monitor, liquid
crystal TV, cellular telephone terminal, GPS terminal, car
navigation system, game machine, bank and convenience-store
terminal and medical diagnostic equipment.
It should be noted that other objects, features and aspects of the
present invention will become apparent in the entire disclosure and
that modifications may be done without departing the gist and scope
of the present invention as disclosed herein and claimed as
appended herewith.
Also it should be noted that any combination of the disclosed
and/or claimed elements, matters and/or items may fall under the
modifications aforementioned.
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